1. Field of the Invention
The present invention relates to a printed circuit board, on which electronic components are mounted, a memory module having the same, and a fabrication method thereof.
2. Description of the Related Art
As electronic products become lighter, thinner, shorter and smaller, semiconductor packages as their core devices are also miniaturized. For miniaturization of the packages, various methods have been proposed and attempted.
Conventionally, a method of miniaturizing the packages may include a Multi-Chip Package (MCP) and a Multi-Chip Module (MCM) on which a plurality of chips or packages are mounted. In the case of the MCM, semiconductor chips and semiconductor packages are mainly mounted on a printed circuit board in a two-dimensional array. In particular, in memory modules which are mounted in a computer as a major application of semiconductor products among the MCM, a plurality of unit memory devices having a desired capacity which are mounted on a printed circuit board by soldering are inserted into a socket of a main body of the computer.
Generally, one to several tens of unit memory devices can be mounted on a single printed circuit board used as a memory module. The unit memory device has a package shape in which a memory chip having a unit memory capacity is mounted therein. In addition, the unit memory device has a structure in which external connection terminals coupled to the memory chip are arranged at the exterior of the package.
However, since the conventional memory module is limited in the number of unit memory devices mounted on the printed circuit board, in order to increase the memory capacity of the memory module, the memory capacity of each unit memory device should be increased. In addition, in order to increase the capacity of a semiconductor chip installed in the unit memory device, it is currently necessary to develop technology for integrating a higher number of cells in a limited space of the semiconductor chip. However, this technology requires a considerable amount of development time due to requirements of precision and finer line width.
More recently, in order to solve these problems, a method of stacking the currently developed memory modules in a three-dimensional array has been proposed. However, when the memory modules are disposed in the three-dimensional array, it results in thermal problems. That is, since the unit memory device mounted on the memory module generates a large amount of heat during operation (when the memory modules are stacked in the three-dimensional array) the thermal problems of the unit memory device cause malfunction of the device at a specific temperature, e.g., about 80° C. or higher.